Panasonic JA751 8" drive question

[Tony Duell]

> Some empirical evidence:

The first thing I would do is trace the ground and +5V rails back to the 
connecotr (if you've not done so already). They should be very easy to find.

> 
> - The unit has a 7812 (12V) 3-terminal regulator hung off what would 

A 7812 is going to need more that 12V input :-)

> normally be the +12V line of the molex connector for, e.g. a 5.25" floppy 
> drive.  That input goes through a 100ohm 5W resistor before hitting the 
> regulator.  With 12V applied the drive, I see only 9.2V at the input to 
> the regulator and approx. 7V on the other side.  Sure _looks_ like maybe 
> it's supposed to see +24V at the top of that resistor, doesn't it?

Indeed it does.

> 
> - With 12V applied, the head-load solenoid doesn't reliably pull in on its 
> own.
> 
> - Head stepper seems a bit anemic.

_Most_ 8" drives have 24V solenoids and motors.

The Archive Sidewinder QIC tape drive has a 4 pin Molex power connector, 
and it uses +5V and +24V (the middle 2 pins being ground). I am told some 
Sun workstations had power cables with molex connnectors on them, most of 
which were +5V and +12V, but one was +5V and +24V for the tape drive. Woe 
betide you if you got that one in the wrong place!

> 
> - I can hear the drive motor slow down from the drag when the heads are 
> loaded.
> 
> - Drive goes through some motions of writing, but won't verify or read 
> anything.
> 
> How luck should I feel?  Should I apply +24V and keep my fingers crossed? 

It's up to you. I'd problaby trace out the scheamtics to see just what 
was going on. But to be honest, with that 7812, it's going to need more 
than 12V, and 24V sounds likely.

-tony